In a multitude of commercial applications, it is common to employ a heavy-duty conveyor belt for the purpose of transporting product and material. The conveyor belts so employed may be relatively long, for example, on the order of miles, and represent a high cost component of an industrial material handling operation. For instance, conveyor belts are widely used for moving minerals, coal, and a wide variety of manufactured products from one point to another. Heavy duty conveyor belts used in mining operations can extend over distances of many miles and represent a high cost component of an industrial material handling operation. For instance, such conveyor belts are often used in typical mining applications to transport minerals below the ground in mines as well as above ground.
Conventional conveyor belts which are used in heavy duty applications are typically comprised of a cured rubber as a top layer, a cured rubber as a bottom layer, and a fabric reinforcement layer (a carcass) which is sandwiched between the top layer and the bottom layer. Conveyor belts used in mining operations can be as large as ten feet wide and up to about three inches thick. The prominent material used in such conveyor belts generally is a moderately flexible elastomeric or rubber-like material, and the belt is typically reinforced by a plurality of longitudinally extending fabric reinforcements or metal cables or cords which are positioned within the belt and extend along the length thereof.
All conveyor belts are, of course, susceptible to normal wear and tear as well as damage from the material being transported and/or harsh environmental conditions. Unfortunately, conveyor belts which are used in mining operations are particularly susceptible to damage from the material transported thereon and a rip, slit, cut or tear may develop on the surface of the belt which comes in contact with the material being transported (the carry cover surface of the belt). For instance, sharp edges of the material being transported, such as iron ore and copper ore which are particularly abrasive, can gouge the surface of the belt and that can result in a rip developing and propagating deeper into the body of the belt. Such damage can ultimately result in belt failure. In the event the conveyor belt suffers catastrophic damage or otherwise becomes inoperable, the costs of repairing the conveyor belt, cleaning up the spilt material, and related downtime can be substantial. In any case, a long service life without the need for continual maintenance and damage repair is highly desirable from the standpoint of cost reduction and efficient utilization of personal and equipment.
Over the years, some improvements have been made in the wear resistance of the rubber cover materials used in manufacturing conveyor belts for transporting highly abrasive materials that quickly wear away conventional rubber conveyor belt covers. However, these improvements have generally only been incremental by virtue of being based upon blends of standard general purpose elastomers, such as styrene-butadiene rubber (SBR), natural rubber, and polybutadiene rubber. In spite of these developments, there remains a long felt need in the mining industry for a premium belt with significantly improved abrasive resistance in order to prolong belt life, reduce mine down-time, and improve productivity. It is also important for such an improved conveyor belt to also retain all other needed performance characteristics to be commercially viable.
One approach to attaining improved abrasion resistance is to incorporate a carry cover layer having improved abrasion characteristics into the conveyor belt. However, it is critical for such a carry cover layer to be capable of being built into the belt in a manner whereby it does not delaminate from the carcass of the belt. In other words, it is critical for such an abrasion resistant material used in making the carry cover layer to exhibit good adhesion to the body of the conveyor belt so that it does not delaminate during the service life of the belt. It is also important for the elastomeric material employed in the carry cover layer to be capable of being compounded in a conventional manner and to be capable of being processed on conventional rubber processing equipment thereby avoiding major capital expenditures. It is also, of course, important for the material to be capable of being used without causing health, safety, and/or environmental issues.